Stack Overflow with recursion circles


I am trying out your framework, looks very good so far. I found a bug which occurs in the following Situation:
I have to 2 classes Referencing each other:
public class User {
public Usergroup{get;set;}
string Name {get;set;}
public class Usergroup {
public IList<User> Users {get;set;}
string Name {get;set;}
Now when doing the following I get a Stackoverflow due to the PropertyChanged Notification for IsValid bubbling back and forth.
var ug = new Usergroup{Name="group1";}
var u = new User {Name="user1";Usergroup = ug};
u,Usergroup = new Usergroup(){Name="group2"}
I did the following to solve the problem, but it's probably not the best solution.
In EntityExtensions.cs I changed RaisePropertyChanged(string proertyName, bool notifyParent) like this:
    private List<IEntityExtensions> visitedParents;
    public void RaisePropertyChange(string propertyName, bool notifyParent)
        if (notifyParent)
            visitedParents= new List<IEntityExtensions>();
    private void RaisePropertyChangedInternal (string propertyName, bool notifyParent){
        var h = PropertyChanged;
        if (h != null)
            h(this, new PropertyChangedEventArgs(propertyName));
        if (notifyParent && Parent != null)
            if (!visitedParents.Contains(Parent))
                ((EntityExtensions)Parent).RaisePropertyChangedInternal(propertyName, true);
                visitedParents = null;

One more thing: In the constructor of EntityBaseTemplate
    protected virtual IEntityExtensions CreateExtensions()
        var entityExtensions = EntityExtensions.RegisterObject(this);
        return entityExtensions;
  there is a call to StartGraphMonitoring, the method doesn't seem to exist anywhere ?
I replaced it with     entityExtensions.StartDirtyTracking();, is that correct ?